With the prosperous development in the electronic semiconductor industry, the progress in the process technique and the trends in the market demands, all kinds of electronic devices have been designed to be compact, low-profile and light in weight. However, while the electronic devices have gradually reduced dimensions, they have increasing functions and computing ability. For example, the notebook computer and the desktop computer, which account for the largest part of products in the information industry, include many electronic elements that would produce heat during the operation thereof. Among others, the central processing unit (CPU) produces the largest part of heat in the computer. Under this circumstance, a heat sink formed from radiating fins and cooling fans for dissipating heat plays an important role in protecting the CPU against overheating, so that the CPU can be maintained at a normal working temperature to fully extend its intended functions. Therefore, the CPU heat sink is a very important component in nowadays information industry.
In recent years, water cooling technique has been widely applied in the personal computer. In the water cooling technique, the large-volume radiating fins are omitted, and heat from the heat sources in the computer system is collected and transferred to the working fluid. Then, the heat-absorbed working fluid exchanges heat with air via a heat exchanger. Since the length of the pipeline for water cooling can be changed according to actual need, the heat exchanger (i.e. the radiating fins) can be flexibly disposed at different positions and can be advantageously designed without spatial restriction. However, a water cooling system requires a pump to drive the working fluid to flow in the pipeline, and a water tank to store sufficient water as the working fluid. That is, the water cooling system is subject to the reliability of the pump, possible leakage in the pipeline, and the like. However, due to the increasing heat produced by the heat-producing element in the personal computer, the water-cooling heat dissipating technique, though not so perfect for use, is still the best choice in the current market for heat management and control. While the water cooling technique can be well applied to the personal computer that has a relatively large volume and is not subject to any spatial restriction, the water cooling technique for heat dissipation seems useless at all in terms of the notebook computer that is compact, low-profile and small volume in design. Therefore, for the present, heat pipes are still used in the notebook computer for heat transfer, and radiating fins are further used to exchange heat with ambient air. Besides the heat pipes and the radiating fins, what the notebook computer can do to protect the CPU is to lower the power consumption of the CPU as much as possible. In view of these problems, the information industry and other related electronic industries all have positively tried to find other heat dissipation techniques capable of providing higher heat flux, so as to meet the growing demands for heat dissipation.
In the conventional heat dissipation techniques, heat pipe and uniform temperature plate are also used as heat transfer elements. In manufacturing the heat pipe and the uniform temperature plate, a sintered layer is formed on the inner wall surface thereof to serve as a wick structure. To form the sintered layer, first fill a type of metal (copper) particles or powder in the inner wall of the heat pipe and the uniform temperature plate, and then tightly press the copper particles or powder before sintering the metal particles or powder in a sinter furnace to form a porous wick structure. While the sintered layer provides a capillary force, it also increases an overall thickness of the heat pipe and the uniform temperature plate, preventing the latter from being effectively slimmed. As to the currently known vapor chamber (VC), it uses a sintered core, grids, or grooves to produce the capillary force for driving steam-water circulation in the heat pipe or the vapor chamber. However, the above structure is not ideal for use because it involves in a very complicated manufacturing process and accordingly, increased manufacturing cost.
Moreover, the selection of a vapor core is not easy. It is very important to select a proper vapor core, which must be able to keep the condensate at a desired flowing speed and must be able to maintain sufficient capillary pressure to overcome any undesired influence from the force of gravity on the vapor and the condensate.
In brief, the prior art heat pipe or vapor chamber has the following disadvantages: (1) uneasy to fabricate; (2) unable to be slimmed; (3) high manufacturing cost; and (4) consuming time and labor to manufacture.